Binocular method utilizing monocular devices

ABSTRACT

A mounting assembly for mounting two monocular devices to form a binocular device. A method of collimating the monocular devices, so that the binocular device is collimated.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of U.S. patent application Ser.No. 09/963,459, filed Sep. 27, 2001.

FIELD OF THE INVENTION

[0002] The present invention is directed to optical devices such asthose used for night vision.

BACKGROUND OF THE INVENTION

[0003] Portable night vision devices are widely used in the military andin law enforcement operations to provide personnel with the ability toview objects at night or during other low light conditions. Thesedevices generally include an objective lens assembly, an imageintensifier tube, and an eyepiece, and typically are physically embodiedin the form of a monocular device which attaches to a helmet orheadband.

[0004] By way of background, a monocular device, as the name implies,has a single optical channel giving an intensified view of the low lightlevel scene to one eye. A biocular device presents the same view to botheyes by means of a dual channel eyepiece. A binocular device, on theother hand, has two monocular channels fixed together to present aslightly different view to each eye. Binocular vision provides improveddepth perception, and there are some night operational missions,including driving land vehicles or boats, where depth perception helpswith the judgment of distances.

[0005] The most widely fielded portable night vision devices are inmonocular form. It would be desirable to be able to take two monoculardevices and quickly assemble a binocular device for those applicationswhere depth perception is necessary. Any such device must have a meansfor allowing adjustment of the distance between the monoculars, known asthe interpupillary distance, to allow for the variation in the distancebetween the eye pupils of different human beings.

[0006] A binocular night vision device needs to have the two intensifiedimages of an object collimated in image space such that the object ispresented to each of the user's eyes at the same azimuth and elevationin the binocular field of view. The two pictures are combined in thebrain to give binocular vision in the same way as such vision isachieved in normal, unaided daytime binocular vision. This combinationof the images is known as binocular fusion. Seeing things with both eyesmakes the image appear to be brighter, clearer, and to give additionaldetail than when it is seen only with one eye. If the object is not seenat the same azimuth and elevation with both eyes there can bedifficulties in obtaining binocular fusion which can lead to eyestrainand headaches. Poor binocular fusion negates the above-mentionedadvantages of using a binocular night vision device. At the presenttime, it is believed that there is no method of ensuring that any twomonocular devices chosen at random would be collimated.

SUMMARY OF THE INVENTION

[0007] It is thus an object of the invention to provide apparatus forforming a binocular device from two monocular devices.

[0008] It is a further object to provide a method of collimatingmonocular devices for use in a binocular device.

[0009] In accordance with an aspect of the invention, apparatus isprovided for forming a binocular device from two monocular devicescomprising a structure having a pair of mounting regions which define adistance therebetween corresponding to a desired, nominal binocularspacing between two monocular devices, and a pair of fasteners, each ofwhich is for removably securing a respective monocular device to amounting region.

[0010] In accordance with a further aspect of the invention, a method ofcollimating monocular devices for use in a binocular device is provided,comprising the steps of:

[0011] rotating the eyepieces of the monocular devices by the samepredetermined amount in the same direction with respect to a fixedreference point on the monocular device;

[0012] providing a mounting means having a right mounting position for amonocular device and a left mounting position opposite the rightposition;

[0013] securing the first monocular device to the mounting means ateither the right mounting position or the left mounting position in suchrotative orientation that if in the right position an object in thecenter of field of view of the monocular device is located slightly leftin azimuth and centered in elevation, and if in the left position anobject in the center of field of view is located slightly right inazimuth and centered in elevation; and

[0014] securing the second monocular device in the mounting means in theopposite position from the first monocular device in a rotativeorientation 180° displaced from the rotative orientation of the firstmonocular device.

[0015] Other aspects of the invention will become apparent by referenceto the following description and claims.

BRIEF DESCRIPTION OF DRAWINGS

[0016] The invention will be better understood by referring to theaccompanying drawings wherein:

[0017]FIG. 1 shows an embodiment of the mounting assembly of theinvention.

[0018]FIG. 2 shows two monocular devices mounted in the embodiment ofFIG. 1.

[0019]FIG. 3 shows the device from the opposite end as FIG. 2.

[0020]FIG. 4 shows how the monocular devices are collimated.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0021] Referring to FIG. 1, an embodiment of a binocular mountingassembly 2 in accordance with the present invention is shown. Beforeproceeding further, it is instructive to refer to FIGS. 2 to 4 to seethe mounting assembly of FIG. 1 with the monocular devices 30 and 32mounted therein. Each monocular device is essentially a unity powertelescope including an image intensifier tube for amplifying low levellight.

[0022] Referring again to FIG. 1, a structure 4 is provided havingmounting regions 6 and 8. The mounting regions are spaced from eachother a distance equal to a desired nominal spacing between themonoculars of a binocular device, and fasteners are secured to themounting regions for removably mounting monocular devices. A centralassembly 7 is provided for attaching the device to a helmet or headband.

[0023] The structure 4 in the embodiment of FIG. 1 is comprised of apair of arms 10 and 12 which connect to the central assembly. Thefasteners in the embodiment of FIG. 1 are mounting blocks 14 and 16, andcorresponding screws 18 and 20.

[0024] Mounting regions 6 and 8 have rails 22 and 24 respectively, builtthereon. Mounting blocks 14 and 16 have grooves 26 and 28 which slide onrails 22 and 24 to accomplish lateral movement of the mounting blocks.Referring to mounting region 6 (mounting region 8 is similar), slot 31is present between the rails. Mounting screw 18 has a first threaded endwhich passes through the slot and is engaged in a threaded hole in amounting area on the monocular, such as mounting projections 25 and 27shown in FIG. 4. Control knob 33 is attached to the second end of screw18. The screws may be captivated in the slots, for example, by means ofE-clips.

[0025] Referring to FIGS. 2 to 4, the monoculars 30 and 32 are attachedto the mounting assembly by positioning them so that the threadedopenings in mounting projections 25 and 27 are aligned with the mountingscrews 18 and 20, and turning the control knobs 33 and 29 to tighten thescrews. Referring again to FIG. 1, each mounting block has a ridge 44which is inserted in a corresponding recess in mounting projections 25and 27 to align the monoculars parallel to each other and preventrotation during installation and operation. The device is also providedwith electrical connectors such as shown at reference numerals 34 and 36for facilitating electrical connection between the monoculars and thecentral assembly. Also, the mounting projections 25 and 27 may havemechanical features which interface with a bracket when the monocular isused as a monocular device.

[0026] The arms 10 and 12 are bent and dimensioned such that mountingregions 6 and 8 are equidistant from the central point of centralassembly 7 in two mutually perpendicular directions, that is from leftto right in FIG. 1 (laterally) and from front to back. The arms areL-shaped, with the first portion of the L-shape extending in theleft-right direction in FIG. 1 and the second portion extending in thefront-back direction. As seen in FIG. 1, the mounting regions are alsoseparated from each other in elevation with respect to the centralpoint.

[0027] Thus, in the operation of the device, monoculars are spaced at adesired nominal distance from each other (the distance between themounting regions or the distance in between the mounting blocks when ina central position on the rails). To adjust the actual interpupillarydistance in order to accommodate different users, the control knobs maybe independently loosened and a monocular device or devices, moved,causing the mounting blocks to slide on the rails to allow adjustment.It is noted that movement of the monoculars is along a straight linepath. When the correct adjustment is achieved, the control knobs aretightened, thus causing the screws to tighten in the monocular devicemounting projections, and causing the mounting block to be compressedagainst the mounting projection and the arm to be compressed against themounting block, to prevent further movement. In an actual device whichwas built, slot 31 and the corresponding slot on the other arm eachallowed 10 mm of lateral adjustment, for a total of 20 mm. The resulting52 to 72 mm interpupillary adjustment is sufficient for 99% ofanthropomorphic variations in interpupillary spacing of the adultpopulation. When the need for a binocular device is finished, themonocular devices may be removed from the mounting assembly by using thecontrol knobs 33 and 29 to remove the screws from the mountingprojections 25 and 27. Thus, the monoculars are restored to theiroriginal status as monocular devices, and may be so used.

[0028] As mentioned above, central assembly 7 is located between thearms for interfacing with a helmet or headband. This may be the sameassembly that is used for interfacing a monocular device with a helmetor headband, so does not require any special adaptation. The mechanicalmeans may be in the nature of a clamp in cavity 52 into which aprojection of the helmet or headband is snapped. The clamp may bereleased by depressing lever 54. Arms 10 and 12 are typically made ofmetal, and may have openings 53 to make the device lighter.

[0029] The fasteners are permanently affixed to the arms, otherwise theywould get lost While an embodiment where the mounting screws andmounting blocks are removable is not recommended, if built suchapparatus would be encompassed herein. While the invention isparticularly applicable to the widely fielded AN/PVS-14 night visionmonocular shown in the Figures herein, other monoculars are encompassedas well.

[0030]FIG. 2 is a view of the device from the objective lens end, whileFIG. 3 is a view of the device from the eyepiece end. Lenses 60 and 62are parts of the eyepiece assemblies through which a user would look tosee the light amplified image. In FIGS. 2 and 3 battery packs 64 and 66are shown as are on/off switch 72 and gain control 74. All of suchfeatures are included in the monocular devices.

[0031] Electrical connections between the central assembly and themonoculars may be provided by means of contacts at the fastenerspreviously described and wiring guided by wire guides 56 which may leadto a magnetic switch in the central assembly. This is for enabling theshut-off on flip-up and shut-off on removal from the mount that arestandard requirements for the previously mentioned AN/PVS-14. Theserequirements are for the image intensifier tubes to become inoperativewhen the helmet mount is moved to the flip-up position and when thedevice is removed from either the headband or helmet mount.

[0032]FIG. 4 shows the binocular device as viewed by a user, and itshould be noted that the left and right monoculars are 180° rotated withrespect to each other. In addition to providing optimal access tocontrols for the specific device shown, this arrangement is key to theability to collimate the device.

[0033] The following is background information relating to thecollimation method of the present invention. Night vision monoculardevices such as the AN/PVS-14 use eyepieces which are similar to thoseused on existing night vision binocular sets (e.g., the AN/AVS-9(V). Ifthe binocular set had no means of adjustment, optical and mechanicalmanufacturing tolerances would affect the optical and mechanicalalignment of both optical channels and the images presented to each eyewould not necessarily coincide in azimuth and elevation. If the imagespresented to each eye did not coincide it would be difficult to achievebinocular fusion on the object, creating the difficulties describedabove. Binocular fusion of both images is assured in the AN/AVS-9(V) bymeans essentially similar to that used in conventional daytimebinoculars. With daytime binoculars an eccentric ring holds the firstlens element in the objective of one of the channels. By rotating theeccentric ring, the image of an object in the center of the field ofview of the eyepiece can be adjusted to be at the same azimuth andelevation as the image seen through the other eyepiece. This process isknown as image collimation. In the event that exact collimation is notpossible, the images are set up to converge. Convergent images are afeature of normal unaided human vision of close objects with, the lefteye looking slightly to the right and the right eye looking slightly tothe left. Convergent images do not adversely affect binocular fusion,because human beings do it all the time. Divergent images, where theeyes have to look outward, are detrimental to binocular fusion, as aredipvergent images where one image is seen above the other.

[0034] AN/AVS-9(V) collimation is achieved by rotating the eyepieces.The lenses in the eyepiece are held in a metal cell, contained by aplastic surround that interfaces with the remainder of the opticalchannel. The mechanical axes of the metal cell and the plastic surroundare deliberately offset by a small amount. Thus, when the eyepiece isrotated, the mechanical axis of the metal cell describes a circle withrespect to the mechanical axis of the plastic surround. As the eyepieceis rotated, the optical axis of the lenses also describes a circle withrespect to the optical axis of the monocular channel. By using opticaltest equipment, it is possible to rotate each eyepiece to bring intocollimation the images of an object seen through each optical channel.As with daytime binoculars, if exact collimation cannot be achieved, theprocedure is to ensure that convergent images result.

[0035] Binocular sets such as the AN/AVS-9(V) are manufactured, operatedand maintained as a binocular. The two optical channels are alwaysassociated with each other, hence collimation is not a problem. On theother hand when a device is manufactured, operated and maintained as amonocular if two such devices are combined to form a binocular, it isstatistically improbable that they would be acceptably collimated.

[0036] The present invention is directed to a procedure for rotating theeyepieces of monoculars to a predetermined orientation duringmanufacture and maintenance. This procedure offsets the image in azimuthand centers it in elevation with respect to a specific orientation ofthe monocular. All monoculars undergo the same set-up procedure. Then,due to the configuration of the mounting assembly, when the monocularsare mounted therein the relative orientation of the monoculars isdisplaced by 180°. Thus, in the right hand monocular of FIG. 4, theeyepiece is rotated such that an image of an object in the center of thefield of view is adjusted to be slightly left in azimuth, and centeredin elevation. The arc and cross shown in the center of each eyepieceillustrates the principle. The cross represents the mechanical axis andthe arrowhead represents the optical axis. The left monocular in FIG. 4is 180° rotated from the right monocular. It's optical axis is offsetslightly right in azimuth and centered in elevation. As a consequence,the binoculars formed by the two monoculars present a convergent imageto both eyes.

[0037] In accordance with a specific set-up procedure, each monocular isplaced on a table with the flat surface of mounting projection 27 beinghorizontal, flush with the table, in the position depicted in FIG. 4.The locking ring which holds the eyepiece in place is loosened, and withthe use of optical test equipment, the entire eyepiece is rotated untilan object in the center of the field of view appears to be slightly leftin azimuth and centered in elevation. All monoculars are similarlyadjusted.

[0038] The result of the procedure is that any monocular combined atrandom with any other monocular would create a collimated,convergent-image binocular that allows binocular fusion of the imagesseen by each eye. The apparatus of the invention is arranged so thatwhen the eyepieces of two monocular devices are similarly adjusted, thedevices will automatically mount with a relative rotative orientationdisplaced by 180°. This is constrained by the structure of the mountingassembly wherein the surfaces of respective movable blocks whichinteract with the mounting areas of the monocular devices face eachother, as depicted in FIG. 4. It should be noted that indicia 80 on theeyepiece is for the purpose of focussing, not collimation. Thus, therotative position of the eyepieces used to effect collimation is notseen in FIG. 4.

[0039] There thus has been described a method and apparatus for forminga binocular device from monoculars. It should be understood that whilethe invention has been disclosed in connection with preferredembodiments, variations will occur to those skilled in the art and areintended to be within the scope of the invention. Thus, the invention tobe covered is defined in the following claims.

We claim:
 1. A method of collimating first and second monocular devicesfor use in a binocular device, comprising the steps of: rotating theeyepieces of both monocular devices by the same predetermined amount inthe same direction with respect to a fixed reference point on themonocular device; providing a mounting means having a right mountingposition for a monocular device and a left mounting position for amonocular device opposite the right position; securing the firstmonocular device to the mounting means at either the right mountingposition or the left mounting position in such rotative orientation thatif in the right position an object in the center of field of view of themonocular device is located slightly left in azimuth and centered inelevation, and if in the left position an object in the center of fieldof view is located slightly right in azimuth and centered in elevation;and securing the second monocular device in the mounting means in theopposite position from the first monocular device in a rotativeorientation 180° displaced from the rotative orientation of the firstmonocular device.
 2. The method of claim 1 wherein each of the first andsecond monocular devices have offset optical and mechanical axes.
 3. Themethod of claim 2 wherein the step of rotating the eyepieces comprisesslightly offsetting an image in azimuth and centering it in elevationwith respect to a fixed orientation of the monocular.
 4. The method ofclaim 3 wherein the monocular devices have mounting projection includinga flat surface, wherein the step of rotating the eyepieces comprisesrotating the eyepieces with the flat surface in a horizontal positionfacing downwardly, and wherein the image in azimuth is offset to beslightly left of center.
 5. The method of claim 3 wherein the mountingmeans is structured so that when identical monocular devices are mountedin the right and left mounting positions respectively, they areconstrained to be in rotative orientations which are displaced by 180°from each other.
 6. The method of claim 5 wherein the monocular deviceshave mounting areas and wherein the mounting means comprises a pair ofarms having respective mounting blocks for interfacing with respectivemounting areas of the monocular devices, and the arms are bent such thatthe respective mounting blocks face each other to thereby determinerelative rotative orientation of the monocular devices.